Committed: fix regression and FAILs with "[PATCH] Don't ignore packed on char bitfields (4.0 regression)"

[Hans-Peter Nilsson <hans-peter dot nilsson at axis dot com>]

> From: Adam Nemet <anemet@caviumnetworks.com>
> Date: Wed, 21 Jan 2009 23:25:16 -0800

> I bootstrapped and regtested again on x86_64-linux and on mips64octeon-linux.
> I will commit this in 24 hours.

You should have made sure to test on a target which has packed
layout by default, as well as a target with #undef PCC_BITFIELD_TYPE_MATTERS.

Your patch changes nothing in the layout for a
non-PCC_BITFIELD_TYPE_MATTERS target, where it has been the same
since at least 3.2.x (which is by itself good :)

> 	* c-decl.c (finish_struct): Move code to set DECL_PACKED after
> 	DECL_BIT_FIELD is alreay known.  Also inherit packed for bitfields
> 	regardless of their type.
> 	* c-common.c (handle_packed_attribute): Don't ignore packed on
> 	bitfields.
> 	* c.opt (Wpacked-bitfield-compat): New warning option.
> 	* stor-layout.c (place_field): Warn if offset of a field changed.
> 	* doc/extend.texi (packed): Mention the ABI change.
> 	* doc/invoke.texi (-Wpacked-bitfield-compat): Document.
> 	(Warning Options): Add it to the list.
> 
> cp/
> 	* class.c (check_field_decls): Also inherit packed for bitfields
> 	regardless of their type.
> 
> testsuite/
> 	* gcc.dg/bitfld-15.c, gcc.dg/bitfld-16.c,
> 	gcc.dg/bitfld-17.c,gcc.dg/bitfld-18.c: New tests.
> 	* g++.dg/ext/bitfield2.C, g++.dg/ext/bitfield3.C,
> 	g++.dg/ext/bitfield4.C, g++.dg/ext/bitfield5.C: New tests.

This patch caused pr17112-1.c to regress for cris-elf, and many
of the new tests FAIL, i.e.:

Running /tmp/hpautotest-gcc1/gcc/gcc/testsuite/gcc.dg/dg.exp ...
FAIL: gcc.dg/bitfld-15.c  (test for warnings, line 10)
FAIL: gcc.dg/bitfld-17.c  (test for warnings, line 9)
...
FAIL: gcc.dg/pr17112-1.c  (test for warnings, line 9)

and

Running /tmp/hpautotest-gcc1/gcc/gcc/testsuite/g++.dg/dg.exp ...
...
FAIL: g++.dg/ext/bitfield2.C  (test for warnings, line 6)
FAIL: g++.dg/ext/bitfield4.C  (test for warnings, line 5)

The fix is trivial, as in the patch below.  It's also obvious
for the new FAILs, but perhaps the regression,
gcc.dg/pr17112-1.c is a surprise.  Since I think that warning is
bogus for a default-packed target(*), I'm happy with this
change, and since at least one maintainer seems to agree, I'm
all too eager to consider it obvious as well.  Though CC:ing
Nathan, as he introduced the warning.

*) See PR38457, which I think your patch solves for the
bit-field case.  (The attribute isn't ignored, it just doesn't
affect the layout.)  As a bonus, got rid of all the bogus fp-bit
warnings!  Still have warnings for non-bitfields, though.

Committed.

testsuite:
	* gcc.dg/bitfld-15.c: Gate warning on target
	pcc_bitfield_type_matters.
	* gcc.dg/bitfld-17.c, g++.dg/ext/bitfield2.C,
	g++.dg/ext/bitfield4.C: Likewise.
	* gcc.dg/pr17112-1.c: Don't expect a warning for the packed
	bitfield for any target.

Index: gcc.dg/bitfld-15.c
===================================================================
--- gcc.dg/bitfld-15.c	(revision 143661)
+++ gcc.dg/bitfld-15.c	(working copy)
@@ -7,6 +7,6 @@
   char a:4;
   char b:8;
   char c:4;
-} __attribute__ ((packed));	/* { dg-message "note: Offset of packed bit-field 'b' has changed in GCC 4.4" "" } */
+} __attribute__ ((packed)); /* { dg-message "note: Offset of packed bit-field 'b' has changed in GCC 4.4" "" {?target pcc_bitfield_type_matters } } */
 
 int assrt[sizeof (struct t) == 2 ? 1 : -1];
Index: gcc.dg/bitfld-17.c
===================================================================
--- gcc.dg/bitfld-17.c	(revision 143661)
+++ gcc.dg/bitfld-17.c	(working copy)
@@ -6,6 +6,6 @@
   char a:4;
   char b:8 __attribute__ ((packed));
   char c:4;
-};				/* { dg-message "note: Offset of packed bit-field 'b' has changed in GCC 4.4" "" } */
+}; /* { dg-message "note: Offset of packed bit-field 'b' has changed in GCC 4.4" "" {?target pcc_bitfield_type_matters } } */
 
 int assrt[sizeof (struct t) == 2 ? 1 : -1];
Index: gcc.dg/pr17112-1.c
===================================================================
--- gcc.dg/pr17112-1.c	(revision 143661)
+++ gcc.dg/pr17112-1.c	(working copy)
@@ -6,7 +6,7 @@
 extern void abort(void);
 
 typedef struct {
-  int int24:24  __attribute__ ((packed)); /* { dg-warning "attribute ignored" "" { target { default_packed && { ! pcc_bitfield_type_matters } } } } */
+  int int24:24  __attribute__ ((packed));
 } myint24;
 
 myint24 x[3] = {
Index: g++.dg/ext/bitfield2.C
===================================================================
--- g++.dg/ext/bitfield2.C	(revision 143661)
+++ g++.dg/ext/bitfield2.C	(working copy)
@@ -3,7 +3,7 @@
 /* { dg-options "" } */
 
 struct t
-{				/* { dg-message "note: Offset of packed bit-field 't::b' has changed in GCC 4.4" "" } */
+{ /* { dg-message "note: Offset of packed bit-field 't::b' has changed in GCC 4.4" "" {?target pcc_bitfield_type_matters } } */
   char a:4;
   char b:8;
   char c:4;
Index: g++.dg/ext/bitfield4.C
===================================================================
--- g++.dg/ext/bitfield4.C	(revision 143661)
+++ g++.dg/ext/bitfield4.C	(working copy)
@@ -2,7 +2,7 @@
 /* { dg-options "" } */
 
 struct t
-{				/* { dg-message "note: Offset of packed bit-field 't::b' has changed in GCC 4.4" "" } */
+{ /* { dg-message "note: Offset of packed bit-field 't::b' has changed in GCC 4.4" "" {?target pcc_bitfield_type_matters } } */
   char a:4;
   char b:8 __attribute__ ((packed));
   char c:4;

brgds, H-P